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Water lettuce in Moore's Creek could spur Indian River Lagoon algae bloom

Pistia (Water lettuce) is an invasive vascular, flowering plant (not an algae) that has proliferated rapidly in Moore’s Creek, as seen on Monday, Jan. 30, 2017, in Fort Pierce.(Photo: CONTRIBUTED PHOTO FROM JIM OPPENBORN)

FORT PIERCE — City staffers and volunteers plan to harvest lettuce, but not the kind you put on a BLT, out of Moore's Creek before it can reach the Indian River Lagoon.

Over the past three weeks, a section of the creek between 10th and 12th streets has become overrun with water lettuce, an invasive flowering plant originally from Africa that looks like Bibb lettuce and floats on top of the water.

The creek empties into the lagoon at the Manatee Observation and Education Center in downtown Fort Pierce. So far, the low-water dam across the creek at 10th Street has kept most of the lettuce from flowing to the lagoon.

But the lettuce-choked water is nearly to the top of the dam, said James B. "Jim" Oppenborn, St. Lucie County coastal resources supervisor, "so a good-sized rain could push it over the top and send the lettuce toward the lagoon."

If a lot of lettuce gets to the lagoon, it could cause problems, said Edie Widder, founder and lead scientist at the Ocean Research and Conservation Association in Fort Pierce.

MORE MUCK

The lettuce will form muck when it dies and sink to the bottom. It also will release nutrients, mostly nitrogen and phosphorus, and that could cause blue-green algae blooms. In fact, one of ORCA's remote-control water sensors at the mouth of Moore's Creek is showing "a significant concentration of blue-green algae," Widder said. "It started Jan. 20, and it's increasing."

The city's public works department will bring in heavy equipment to scoop up the lettuce, said City Commissioner Jeremiah Johnson.

"But they can only dip and scoop so much," he added. "They're going to need volunteers to help push the lettuce toward the equipment."

Volunteers probably will use a combination of seines and yard rakes to get as much of the lettuce as possible into the scoopers and out of the creek.

"Water lettuce floats on top of the water; it isn't fixed to the bottom," Johnson said. "So it should be relatively easy to, what I call, 'feed the machine.'"

WANT TO HELP?

What: Remove water lettuce from Moore's Creek

When: 9 a.m. to noon Saturday, Feb. 11

Where: 10th Street Bridge across Moore's Creek

What to expect: Volunteers will push water lettuce toward machinery that will scoop it out of the water